1 /*
2 * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the author nor the names of any co-contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $FreeBSD$
30 */
31
32 #include "namespace.h"
33 #include <pthread.h>
34 #include "un-namespace.h"
35 #include "thr_private.h"
36
37 __weak_reference(_pthread_once, pthread_once);
38
39 #define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT
40 #define ONCE_DONE PTHREAD_DONE_INIT
41 #define ONCE_IN_PROGRESS 0x02
42 #define ONCE_MASK 0x03
43
44 static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER;
45 static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER;
46
47 /*
48 * POSIX:
49 * The pthread_once() function is not a cancellation point. However,
50 * if init_routine is a cancellation point and is canceled, the effect
51 * on once_control shall be as if pthread_once() was never called.
52 */
53
54 static void
once_cancel_handler(void * arg)55 once_cancel_handler(void *arg)
56 {
57 pthread_once_t *once_control = arg;
58
59 _pthread_mutex_lock(&once_lock);
60 once_control->state = ONCE_NEVER_DONE;
61 _pthread_mutex_unlock(&once_lock);
62 _pthread_cond_broadcast(&once_cv);
63 }
64
65 int
_pthread_once(pthread_once_t * once_control,void (* init_routine)(void))66 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
67 {
68 struct pthread *curthread;
69 int wakeup = 0;
70
71 if (once_control->state == ONCE_DONE)
72 return (0);
73 _pthread_mutex_lock(&once_lock);
74 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
75 _pthread_cond_wait(&once_cv, &once_lock);
76 /*
77 * If previous thread was canceled, then the state still
78 * could be ONCE_NEVER_DONE, we need to check it again.
79 */
80 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
81 once_control->state = ONCE_IN_PROGRESS;
82 _pthread_mutex_unlock(&once_lock);
83 curthread = _get_curthread();
84 THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
85 init_routine();
86 THR_CLEANUP_POP(curthread, 0);
87 _pthread_mutex_lock(&once_lock);
88 once_control->state = ONCE_DONE;
89 wakeup = 1;
90 }
91 _pthread_mutex_unlock(&once_lock);
92 if (wakeup)
93 _pthread_cond_broadcast(&once_cv);
94 return (0);
95 }
96
97